A permanent magnet electric motor of an inner rotor type is known in which a rotor having permanent magnets is rotatably disposed inside a stator that generates a rotating magnetic field. This permanent magnet electric motor is used, for example, for rotating a blower fan mounted on an air conditioner. When this permanent magnet electric motor is driven by a PWM inverter that performs high-frequency switching, a potential difference (axial voltage) occurs between the inner ring and the outer ring of the bearing, and when this axial voltage reaches the breakdown voltage of the oil film inside the bearing, current flows inside the bearing to cause electrolytic corrosion inside the bearing. To prevent this electrolytic corrosion of the bearing, for example, a permanent magnet electric motor provided with a rotor having an insulating member is known.
This rotor is provided with, for example, a plurality of permanent magnets annularly arranged at regular intervals, an annular outer periphery side iron core disposed on the inner diameter side of the plurality of permanent magnets, an annular inner periphery side iron core disposed on the inner diameter side of the outer periphery side iron core, an insulating member formed of a resin between the outer periphery side iron core and the inner periphery side iron core and insulating the outer periphery side iron core and the inner periphery side iron core from each other, and a shaft fixed to a through hole passing through along the central axis of the inner periphery side iron core.
As a rotor constructed like this, a structure is known in which the outer periphery side iron core is provided with a plurality of outer periphery side rotation locking concave portions that are concave from the inner periphery toward the outer diameter side and formed at regular intervals in the circumferential direction, the inner periphery side iron core is provided with a plurality of inner periphery side rotation locking concave portions that are concave from the outer periphery toward the inner diameter side and formed at regular intervals in the circumferential direction and by the insulating member being filled in the outer periphery side rotation locking concave portions and the inner periphery side rotation locking concave portions, the rotation locking of the outer periphery side iron core and the inner periphery side iron core with the insulating member is performed (for example, see JP-A-2015-106928).
In the structure disclosed in JP-A-2015-106928, when a plurality of outer periphery side rotation locking concave portions are formed so as to be concave from the inner periphery toward the outer diameter side as the outer periphery side iron core of the rotor, since the thickness in the radial direction of the outer periphery side iron core is small at the parts of the outer periphery side rotation locking concave portions, there is a possibility that strength decrease occurs at these parts of the outer periphery side rotation locking concave portions.
Because of such strength decrease at the parts of the outer periphery side rotation locking concave portions, for example, there is a possibility that the outer periphery side iron core is deformed in the radial direction at the parts of the outer periphery side rotation locking concave portions by the molding pressure when the outer periphery side iron core, the inner periphery side iron core and permanent magnets are disposed inside a metal mold and a resin is poured into the metal mold to mold the insulating member. When the outer periphery side iron core is deformed, the inner periphery side of the permanent magnet is stressed, so that there is a possibility that a crack occurs on the permanent magnet to break the permanent magnet.